Electrochemical Insertion Properties of the Novel Lithium Vanadium Fluorophosphate, LiVPO[sub 4]F

Abstract

The novel fluorophosphate compound, Å, Å, Å, has been synthesized by a novel two-step reaction method based on a carbothermal reduction (CTR) process. In the initial CTR step, vanadium pentoxide, ammonium dihydrogen phosphate, and a high surface area carbon are reacted under an inert atmosphere to yield the trivalent vanadium phosphate, The transition-metal reduction is facilitated by the high temperature carbothermal reaction based on the transition. These CTR conditions favor stabilization of the vanadium as as well as leaving residual carbon, which is useful in the subsequent electrode processing. In the second incorporation step, the CTR is reacted with LiF in an argon atmosphere to yield the single phase product. Preliminary electrochemical evaluation of the carried out at 23°C indicates a reversible specific capacity of around 115 mAh/g, a performance roughly equivalent to cycling of in Elevated temperature testing suggests that the extraction process may yield the novel delithiated phase, High resolution measurements reveal a structured voltage response for the lithium extraction process characterized by two well-defined peaks in the differential capacity data. The corresponding discharge process, centered at around 4.19 V vs. Li, indicates a two-phase reaction mechanism coupled to phase nucleation behavior. The insertion properties of the are compared with the other vanadium-based polyanion materials, namely and The demonstrated performance suggests that the insertion system may offer some properties favorable for commercial application. © 2003 The Electrochemical Society. All rights reserved.